How the heck can I redeem the minecoins I've bought?!!!!

I've been going around in circles ALL DAY and I can't figure out how to get an answer, I just get the same articles that don't help.

It took ages to figure out how to buy Minecoins in the first place.

Then I found a way and got a voucher code thing.

Then told to put the 12-digit code into the Playstation store, but my codes are longer than 12 numbers!

I managed to redeem one of the codes on my Microsoft account, the other wasn't recognised. But now how do I link that to my daughter's PS4 account?

Why is this all so hard????